Device for continuous supply of a liquid



Feb. 21, 1956 r Wu; 2,735,440

DEVICE FOR CONTINUOUSLSUPPLY OF A LIQUID Filed Feb. 12, 1954 17 '5 ,2 i:% 1 J I L16 3? Z? 23 m *I m INVE N TOR KARL TORSTEN KA'LLE United States Patent O 2,735,440 DEVICE FOR CONTINUOUS SUPPLY OF A LIQUID Karl Torsten Kiille, Saflle, Sweden Application February 12, 1954, Serial No. 409,993 6 Claims. (Cl. 137-87) The invention relates to a device for the continuous supply of a liquid, particularly for the continuous supply of a predetermined amount of a liquid to any medium.

When supplying solutions of chemicals or dyes continuously to a medium, it is often desired to vary the mutual ratio between the substances added and also the total amount of the additions in dependence on variations in the amount of such medium. Previously it has been customary to use piston pumps for supplying liquids. One or more such pumps have then been connected to a common, motor-driven shaft, the speed of which has been varied in dependence on varying amounts of the' medium to which the additions are to be made. The mutual ratio between the solutions added has been varied by adjusting the lengths of the piston strokes. When such an adjustment is to be carried out continuously, very complicated and expensive arrangements are necessary, and also complicated regulating means are required to vary the speed of the piston movement in dependence on some physical change of said medium.

The object of the invention is to provide a device making possible a predetermined and constant supply of any liquid.

Another object of the invention is to provide a device by which a liquid may be continuously supplied to a medium in exact proportion to varying amounts of said medium.

The device according to the invention comprises a' rotary pump, an inlet for the liquid and an inlet for gas to the suction side of the pump, an outlet for the mixture of liquid and gas from the pressure side of the pump, a restricted passage in this outlet, an adjustable valve connected to the gas inlet for determining the proportion of gas sucked by the pump, and a pressure responsive element subjected to the pressure before the restricted outlet passage and actuating the valve to open in dependence on said pressure at the outlet, whereby the proportions of liquid and gas discharged will be kept substantially constant.

The device according to the invention will be more closely described with reference to the accompanying drawing which shows a preferred embodiment. 1 designates a gear pump. A pipe 2 from the suction side of the pump leads to a container 3 adapted to contain is to be supplied continuously. A branch pipe 4 extends from the suction side of the pump and is connected to a valve housing 6 by means of a flexible hose of rubber or the like. Said valve housing is supported by a pressure responsive member to be moved by it in vertical direction. In the embodiment shown a Bourdon pipe 7 has its closed end fixed to the valve housing, while its open end is mounted on a fixed support 9 and communicates with a conduit 8. Moreover, the valve housing is suspended in a spring 10 which is fixed to a set screw 12 inserted in a support 11, whereby the elevation of the housing can be adjusted, if desired. The conduit 8 has a restricted inlet 13 and is intended to be connected to a source of compressed gas, preferably having a constant pressure. The purpose of the restricted inlet is to eliminate the action a liquid which of possible minor variations of the gas pressure. A pressure gauge 14 is connected to the conduit 8 between the restricted passage 13 and the Bourdon pipe 7. A branch conduit 15, preferably of a considerably smaller cross section than conduit 8, extends from a point between the pressure gauge and the restricted passage to a vessel 16. Said vessel has an inlet conduit 31 for liquid and an outlet pipe 30 controlled by a cock 29. A liquid flows continuously through said vessel and the open end of the conduit 15 has to be submerged under the liquid level.

A pipe 18 from the pressure side of the pump opens into the vessel 16 to supply liquid from the container 3. The pipe 18 has a restricted passage 17 close to the pump.

Another conduit 19 leads from the pressure side of the pump to the open end of a Bourdon pipe 21 serving as a pressure responsive member. A pressure gauge 22 is inserted into the conduit 19 to indicate the pressure therein. The end of the Bourdon pipe connected to the conduit 19 is mounted on a fixed base 20 and the opposite, closed end of said pipe 21 carries a rod supporting the valve member 23 of the valve housing 6. When the device is not operated, said valve member 23 is pressed against its seat by means of a compression spring 26 inserted between the outside of the housing 6 and a stop member 24 provided on the valve spindle 25. The action of said spring 26 is partly counteracted by a spring 27 mounted between the valve spindle and a set screw 28 which is inserted in the support 11.

The device described operates as follows. The pump 1 is driven at a constant speed by means of a motor, not shown, and consequently it sucks a constant volume per unit of time. Initially, the pressures at the suction side and the pressure side of the pump are equal, i. e. equal to the atmospheric pressure, and the valve member 23 is closed. When the pump begins to operate, it sucks liquid through the conduit 2, and owing to the restricted passage 17 of the outlet conduit 18 a certain over-pressure then arises at the pressure side of the pump.. This overpressure propagates through the conduit 19 to the pressure responsive member or Bourdon pipe 21 which is thereby somewhat straightened and depresses the valve member 23, so that the valve is opened to supply air or another gas through the conduit 4. As an under-pressure is prevailing at the suction side of' the pump, gas will be sucked in" and pass the pump" mixed with the liquid. As men tioned above, the pump sucks a constant volume per unit of time and, therefore, the total volume of transported liquid and gas will be constant, only the proportion of the two media being changed. The gas passes the restriction 17 considerably more easily than the liquid, and thus the pressure in the conduit 19 will be lower than if only liquid is fed through the pump. When the pressure drops at the pressure side of the pump, the valve 6 is somewhat throttled to let in a smaller amount of gas. Rather soon a state of equilibrium is reached as to the proportions of liquid and gas in the mixture, and the actual proportions will be dependent on the position of the set screw 28. By adjusting said screw the action of the spring 27 upon the valve member 23 will be decreased or increased, and thus it is evidently possible to change the amount of liquid supplied to the vessel 16.

At a constant adjustment of the cock 29 in the outlet 3%), the liquid level in the vessel 16 will vary directly with the amount of liquid supplied through the inlet conduit 31, and the amount of liquid delivered through conduit 18 will be directly proportioned to the amount of liquid supplied through conduit 31, and the amount discharged through the pipe 30 will be dependent on the static pressure of the liquid in the vessel. When, for instance, the liquid level rises in the vessel 16, the resistance to the outflow of gas from the conduit 15 is increased, so that also the pressure in the conduit 8 after the restricted passage 13 and in the Bourdon pipe 7 will increase. This results in a slight lowering of the valve housing 6, where by the supply of gas to the suction side of the pump is throttled, and consequently the pump will transport a greater amount of liquid to the vessel 16. Thus, as the liquid level rises in vessel 16 from an increased amount of liquid delivered through conduit 31, a proportionally increased amount of liquid will be delivered through conduit 18.

If several liquids are to be supplied to the liquid in the vessel 16, the pumps required for this purpose may be coupled to one common driving shaft. The mutual ratio between the liquids supplied may then be adjusted by means of the set screw 28.

From the specification above it is evident that the device described is on the Whole useful for continuously supplying a predetermined and constant amount of any liquid, and this amount may be adjusted manually, as desired. On the other hand, the device is also useful for continuously adding an exactly proportionated amount of liquid to a flow of another liquid, the amount of which may vary from time to time. The device is rather insensitive to such possible slight variations of the speed of the pump, which are caused by variations as to the periodicity of the electric current, as the pressure arising at the pressure side of the pump always determines the amount of liquid passing the pump. Consequently, possible leakages have no importance whatever, provided the pump has a sufficient capacity.

What I claim is:

1. A device for continuous supply of a liquid, comprising a rotary pump, an inlet for the liquid and an inlet for gas to the suction side of the pump, an outlet for the mixture of liquid and gas from the pressure side of the pump, a restricted passage in this outlet, an adjustable valve connected to the gas inlet for adjusting the proportion of gas sucked by the pump, and a pressure responsive element subjected to the pressure before the restricted outlet passage and actuating the valve to open in dependence on said pressure, whereby the quantity of liquid discharged will be kept substantially constant.

2. A device according to claim 1, in which said pressure responsive element consists of a Bourdon pipe having its open end connected to the pressure side of the pump, said end being mounted on a fixed support, while the opposite closed tube end is connected to a movable member of the valve.

3. A device for continuous supply of liquid to a flow of medium, comprising a rotary pump, an inlet for the liquid and an inlet for gas to the suction side of the pump, an outlet for the mixture of liquid and gas from the pressure side of the pump having a restricted portion therein, an adjustable valve connected to the gas inlet for adjusting the proportion of gas sucked by the pump, a first pressure responsive element subjected to the pressure ahead of the restricted outlet passage and connected to said adjustable valve to open said valve in dependence on said pressure to keep the quantity of liquid discharged substantially constant at a constant flow of the medium, and a second pressure responsive element subjected to the pressure of the flowing medium and connected to said adjustable valve to adjust said valve in dependence on pressure variations of said flowing medium to adjust the amount of gas supplied to the suction side of said pump and thereby adjust the amount of liquid supplied to the flowing medium from said pump.

4. A device as claimed in claim 3 in which the first pressure responsive element comprises a Bourdon pipe having its open end connected to the pressure side of the pump, and a fixed support on Which said end is mounted, the closed end of said pipe being connected to said adjustable valve.

5. A device as claimed in claim 3 in which said second pressure responsive element comprises a Bourdon pipe, and a fixed support on which the open end of said pipe is mounted, a source of compressed gas, a conduit lead ing from said source to the open end of said Bourdon pipe, the closed end of said pipe being connected to said adjustable valve, said compressed gas conduit having a restricted passage therein, and a branch conduit from a point between said restricted passage and the Bourdon pipe having an open end submerged under the liquid level of said flowing medium.

6. A device as claimed in claim 3 in which said adjustable valve comprises a housing, a valve member adjustable therein, said housing and valve member each being supported by one of said pressure responsive elements to be moved by them in relation to each other, and a flexible conduit from said housing to said gas inlet.

References Cited in the file of this patent UNITED STATES PATENTS 

